Raman spectroscopy of the system iron(III)-sulfuric acid-water: an approach to Tinto River's (Spain) hydrogeochemistry

Acid mine drainage is formed when pyrite (FeS(2)) is exposed and reacts with air and water to form sulfuric acid and dissolved iron. Tinto River (Huelva, Spain) is an example of this phenomenon. In this study, Raman spectroscopy has been used to investigate the speciation of the system iron(III)-sulfuric acid-water as an approach to Tinto River's aqueous solutions. The molalities of sulfuric acid (0.09 mol/kg) and iron(III) (0.01-1.5 mol/kg) were chosen to mimic the concentration of the species in Tinto River waters. Raman spectra of the solutions reveal a strong iron(III)-sulfate inner-sphere interaction through the nu(1) sulfate band at 981 cm(-1) and its shoulder at 1005 cm(-1). Iron(III)-sulfate interaction may also be facilitated by hydrogen bonds and monitored in the Raman spectra through the symmetric stretching band of bisulfate at 1052 cm(-1) and a shoulder at 1040 cm(-1). Other bands in the low-frequency region of the Raman spectra are attributed to the hydrogen-bonded complexes formation as well.     

TRLFS study on the speciation of uranium in seepage water and pore water of heavy metal contaminated soil

In situ leaching of uranium ores with sulfuric acid during active uranium mining activity on the Gessenheap has caused longstanding environmental problems of acid mine drainage and elevated concentrations of uranium. To study there remediation measures the test site Gessenwiese, a recultivated former uranium mining heap near Ronnenburg/East Thuringia/Germany, was installed as a part of a research program of the Friedrich-Schiller University Jena to study, among other techniques, the phytoremediation capacity of native and selected plants towards uranium. In the first step the uranium speciation in surface seepage and soil pore waters from Gessenwiese, ranging in pH from 3.2 to 4.0, were studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Both types of water samples showed mono-exponential luminescence decay, indicating the presence of only one major species. The detected emission bands were found at 477.5, 491.8, 513.0, 537.2, 562.3, and 590.7 nm in case of the surface water samples, and were found at 477.2, 493.2, 513.8, 537.0, 562.4, and 590.0 nm in case of the soil water samples. These characteristic peak maxima together with the observed mono-exponential decay indicated that the uranium speciation in the seepage and soil pore waters is dominated by the uranium (VI) sulfate species UO₂SO_4(aq). Due to the presence of luminescence quenchers in the natural water samples the measured luminescence lifetimes of the UO₂SO_4(aq) species of 1.0–2.6 μs were reduced in comparison to pure uranium sulfate solutions, which show a luminescence lifetime of 4.7 μs. These results convincingly show that in the pH range of 3.2–4.0 TRLFS is a suitable and very useful technique to study the uranium speciation in naturally occurring water samples.     

Vibrational spectra of copper sulfate hydrates investigated with low-temperature Raman spectroscopy and terahertz time domain spectroscopy

In this paper, the vibrational spectra of copper sulfate hydrates (CuSO(4)·xH(2)O, x = 5, 3, 1, 0) have been investigated with low-temperature Raman spectroscopy and terahertz time domain spectroscopy (THz-TDS). It is found that the four groups of Raman bands between 90 and 4000 cm(-1) can be assigned to lattice vibration as well as intramolecular vibrations of a copper complex, sulfate group, and water molecules. The variation of vibrational spectra during the dehydrated process are discussed in detail considering the transformation of the crystal structure, especially the bands between 3000 and 3500 cm(-1), which are attributed to the ν(1) and ν(3) modes of water molecules. In addition, as a complement of Raman spectra, the THz spectra at 0.1-3 THz indicate the absorption due to the low-frequency lattice vibration and hydrogen bond.     

Influence of phosphate modification on the surface properties of sulfated titania

The effect of increasing phosphate loading on the bulk and surface properties of sulfated titania was investigated by thermogravimetry, X-ray diffraction, laser Raman spectroscopy and FT-IR spectroscopy. The acid properties of the material were probed by low-temperature FT-IR spectroscopy of adsorbed CO. Monophosphate species in varying symmetries and protonation states were detected on the surface of the sulfated titania at low loadings. These condensed with formation of surface polyphosphates with increasing loading. Phosphate blocks weak Lewis acid sites and partially displaces sulfate groups. While the acid, properties of phosphate-free sulfated titania are dominated by Lewis acid sites, the phosphated samples also developed Brønsted acid sites due to the presence of POH groups on the surface.     

Spectroscopic study on the precipitation of sodium alkyl sulfate with cetylpyridinium chloride

The precipitation of sodium alkyl sulfate with cetylpyridinium chloride was obtained under optimized conditions. The conditions for the most efficient formation of precipitates were obtained as longer alkyl chain length of alkyl sulfate (C(14)), higher pH (pH 12), 1.5 M NaCl, and equimolar ratio between anionic and cationic surfactants. The structures and physical properties of surfactant precipitates were investigated with SEM, UV-vis, and FT-IR spectroscopy and light scattering. The precipitate of sodium alkyl sulfate with cetylpyridinium chloride was studied with the pressure-area isotherm at the air/water interface. In addition, the surface morphology of the Langmuir-Blodgett film of surfactant precipitate was observed with atomic force microscopy.     

Micro-Raman studies of hydrous ferrous sulfates and jarosites

Ferrous sulfates of various hydration states (FeSO(4) X xH(2)O; x=7, 4, 1) and jarosites (MFe(3)(SO(4))(2)(OH)(6); M=Na or K) were synthesized and studied by micro-Raman spectroscopy between 295 and 8K. Spectral analyses of the sulfate and water/hydroxyl vibrational modes are presented. Fingerprint regions attributed to the symmetric (nu(1)) and antisymmetric (nu(3)) stretching vibrations of the sulfate group are found to vary with the degree of hydration in hydrous ferrous sulfate. In jarosites, the Raman shift of the OH stretching mode is related to the type of alkali metal present between the tetrahedral and octahedral layers. The Raman technique can thus unambiguously identify ferrous sulfate of various hydration states and jarosites bearing different alkali metal ions.     

Solid/Liquid phase diagram of the ammonium sulfate/maleic acid/water system

We have studied the low temperature phase diagram and water activities of the ammonium sulfate/maleic acid/water system using differential scanning calorimetry and infrared spectroscopy of thin films. Using the results from our experiments, we have mapped the solid/liquid ternary phase diagram, determined the water activities based on the freezing point depression, and determined the ice/maleic acid phase boundary as well as the ternary eutectic composition and temperature. We also compare our results to the predictions of the extended AIM aerosol thermodynamics model and find good agreement for the ice melting points in the ice primary phase field of this system; however significant differences were found with respect to phase boundaries, maleic acid dissolution, and ammonium sulfate dissolution.     

基于多光谱特征融合技术的面粉掺杂定量分析方法

提出了一种基于拉曼光谱技术(Raman)和激光诱导击穿光谱技术(LIBS)的多光谱特征融合技术(MFFT),利用拉曼光谱中分子组分信息和激光诱导击穿光谱中原子组分信息之间的互补特性,采用自适应小波变换(AWT)-竞争性自适应加权(CARS)-偏最小二乘回归(PLS)建模技术,获取了面粉体系更为全面的特征信息。在多光谱特征融合技术中,首先采用AWT-CARS方法分别提取拉曼光谱和激光诱导击穿光谱中的特征变量,然后将两者的特征变量融合为一个向量,采用PLS方法构建MFFT模型,实现了面粉掺杂物的定量分析。通过对二氧化钛、硫酸铝钾等面粉掺杂体系建模分析,考察MFFT模型的有效性。结果表明,与单一拉曼光谱技术或激光诱导击穿光谱技术建立的预测模型相比,MFFT模型显著提升了模型的预测性能,二氧化钛和硫酸铝钾预测模型的线性相关系数分别从相对较差的Raman模型的0.884、0.877提升到0.981、0.980,其预测均方根误差分别从相对较差的Raman模型的0.151、0.154降低到0.069、0.068。表明多光谱特征融合技术可以准确提取Raman光谱中的分子信息和LIBS光谱中的元素信息,使其互为补充、互为校正,进而有效克服面粉基质对掺杂组分定量分析的干扰,显著提高模型的预测精度。     

The characteristics of the nanosized η-TiO2 polymorph

The nanosized η-TiO₂ polymorph was prepared by the hydrolysis of titanyl sulfate (TiO)SO₄ · xH₂SO₄ · yH₂O. η-TiO₂ was studied by X-ray diffraction, X-ray photoelectron spectroscopy, IR spectroscopy, and Raman spectroscopy. Characteristic X-ray data and distinguishing Raman spectrum features were found for η-TiO₂,. The surface of η-TiO₂ samples contained adsorbed OH⁻ particles and water molecules or water molecules of crystal hydrates. The free specific surface area of samples with crystallite sizes of L = 50 (4) and 60 (5) ? was S = 10.17 (9) and 15.6 (1) m²/g. The characteristics of samples with η-TiO₂ were favorable for their use as photocatalysts and adsorbents.     

Deliquescence and efflorescence behavior of ternary inorganic/organic/water aerosol particles

The deliquescence behavior of ternary inorganic (ammonium sulfate and ammonium nitrate)/organic (glutaric acid and malonic acid)/water aerosol particles has been investigated at 293 K using a novel surface aerosol microscopy (SAM) technique. The results obtained for the deliquescence relative humidities (DRH) for particles of variable inorganic/organic contents show a eutectic behavior with the mixed particles showing deliquescence at lower DRH compared to the pure inorganic and organic components, respectively. This behavior has been quantitatively modeled using the extended aerosol inorganics (E-AIM) thermodynamic model of Clegg et al. in combination with the UNIFAC group activity approach to account for organic molecular solutes. In addition, we have investigated the crystallization behavior of supersatured and formerly deliquesced ternary solution droplets using space resolved Raman spectroscopy. It is found that such droplets produce solid particles in which the inorganic and organic phases show some spatial separation with the organic component being predominantly found at the outer part of the particle. Independent measurements of the contact angles of such ternary droplets reveal that their angles are within experimental error identical to those of the purely organic/water solutions.     

Solid/liquid phase diagram of the ammonium sulfate/malic acid/water system

We have studied the low temperature phase diagram and water activities of the ammonium sulfate/malic acid/water system using differential scanning calorimetry (DSC) and infrared spectroscopy (IR) of thin films. Using the results from our experiments we have mapped the ice primary phase region of the solid/liquid ternary phase diagram. In our DSC and IR experiments we observe ice nucleation in all samples and ammonium sulfate in some samples, which were cooled to 183 K. However, we only observed malic acid nucleation in IR experiments, where the sample was in contact with ZnSe windows. We also compare our results to the predictions of the Extended AIM Aerosol Thermodynamics Model (E-AIM) and find good agreement for the ice melting points in the ice primary phase field of this system; however, the E-AIM has difficulty predicting malic acid crystallization.     

Sulfate Ions in Titania Polymorphs

Sol-gel titania was sulfated by using sulfuric acid as hydrolysis catalyst, or by impregnating with ammonium sulfate fresh samples prepared with nitric acid or ammonium hydroxide as hydrolysis catalyst. Samples were characterized with X-ray powder diffraction, infrared spectroscopy, thermogravimetry and atomic absorption spectroscopy. Sulfate ions were found anchored to brookite and anatase phases, because they have short O—O atomic bond lengths slightly larger than the largest O—O bond length of sulfate ion. Since the shortest O—O atomic bond in anatase is smaller than the one in brookite, the sulfate ions are then less deformed when they are anchored to anatase, and consequently more stable. Therefore when the sample temperature is raised, the brookite with sulfate ions was transformed mainly to anatase and not into rutile, which is the most probably transformation when these ions are not involved. Sulfate ions also hindered anatase and brookite crystallite growing and stabilized the crystalline structure of anatase. When the sulfate ions are lost the crystalline anatase phase is transformed into rutile, leaving a large number of vacancies that favored atom diffusion and consequently the growing of rutile crystallites. The crystalline evolution of the samples as a function of the annealing temperature is almost independent of the sulfating method.     

Rare earth elements in mine,slime, and river waters in the Kavalerovsky and Dalnegorsky districts of the Russian Far East

The concentrations of rare earth elements (REEs) in anthropogenic (mine and slime) and river waters of Kavalerovsky and Dalnegorsky districts of the Far East have been estimated. The highest concentrations of REs have been found in mine water of the Dubrovskoe deposit (Kavalerovsky district), especially in the slime waters of the old tailing dump of the Krasnorechenskaya ore-dressing plant (KODP, Dalnegorsky district). Contamination of the Rudnaya river water has been detected in the vicinity of the KODP old and new tailings dumps. Taking into account that REEs are concomitant with sulfide minerals, the former can be extracted by repeated processing of wastes from the KODP old and new tailings dumps.     

Effects of bacterially produced precipitates on the metabolism of sulfate reducing bacteria during the bio-treatment process of copper-containing wastewater

A large volume of bacterially produced precipitates are generated during the bio-treatment of heavy metal wastewater. The composition of the bacterially produced precipitates and its effects on sulfate reducing bacteria (SRB) in copper-containing waste stream were evaluated in this study. The elemental composition of the microbial precipitate was studied using electrodispersive X-ray spectroscopy (EDX), and it was found that the ratio of S:Cu was 1.12. Combining with the results of copper distribution in the SRB metabolism culture, which was analyzed by the sequential extraction procedure, copper in the precipitates was determined as covellite (CuS). The bacterially produced precipitates caused a decrease of the sulfate reduction rate, and the more precipitates were generated, the lower the sulfate reduction rate was. The particle sizes of bacterially generated covellite were ranging from 0.03 to 2 μm by particles size distribution (PSD) analysis, which was smaller than that of the SRB cells. Transmission electron microscopy (TEM) analysis showed that the microbial covellite was deposited on the surface of the cell. The effects of the microbial precipitate on SRB metabolism were found to be weakened by increasing the precipitation time and adding microbial polymeric substances in later experiments. These results provided direct evidence that the SRB activity was inhibited by the bacterially produced covellite, which enveloped the bacterium and thus affected the metabolism of SRB on mass transfer.     

The analysis of nitrate in environmental samples by reversed-phase HPLC

A method is presented for the analysis of nitrate in natural waters and waste water by high-performance liquid chromatography (HPLC) with a reversed-phase octadecyl column, aqueous phosphoric acid/dihydrogen phosphate mobile phase, and UV detector. The optimum nitrate concentration is 0.3 to 3 mg/L as N with linear detector response below 3 mg/L. The detection limit is 0.007 mg/L. Relative standard deviations in the optimum range are consistently less than one percent. Several potential interferences have been investigated; nitrite and organic chromophores are resolved from nitrate and do not interfere. Hexavalent chromium and sulfate are slight positive interferences, negligible at typical environmental concentrations. The method produces results in agreement with the accepted chromotropic acid method except in samples from eutrophic lakes, for which evidence is presented indicating that the chromotropic acid is inaccurate.     

Characterization of mesoporous nanocrystalline TiO2 photocatalysts synthesized via a sol-solvothermal process at a low temperature

Nanocrystalline TiO₂ samples with mesoporous structure were prepared via a solvothermal treatment of surfactant-stabilized TiO₂ sols. The samples were obtained from media of different acidities including nitric acid, deionized water, and ammonia (denoted as HT-1, HT-2 and HT-3, respectively). These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N₂-sorption (BET surface area), micro-Raman spectroscopy, infrared absorption spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were tested by the self-photosensitized degradation of an azo dye, Mordant Yellow 10 (MY), in aqueous solution under visible light irradiation. The results reveal that all three samples have high surface area and are pure anatase phase. The sample prepared in nitric acid medium possesses the most ideal mesoporous structure and also exhibits a blue shift in the Raman spectrum. All three samples show much higher photocatalytic activity than the commercial P-25. The activity order of the three samples is HT-1>HT-2>HT-3.     

Quantum Effects on Global Structure of Liquid Water

The structure difference between light and heavy liquid water has been systematically in-vestigated by high precision Raman spectroscopy over the temperature range of 5-85 oC. Distinct difference between the Raman spectral profiles of two different liquid waters is clearly observed. By analyzing the temperature-dependent Raman spectral contour using global fitting procedure, it is found that the micro-structure of heavy water is more ordered than that of light water at the same temperature, and the structure difference between the light and heavy water decreases with the increase of the temperature. The temperature off-set, an indicator for the structure difference, is determined to vary from 28 oC to 18 oC for the low-to-high temperature. It indicates that quantum effect is significantly not only at low temperature, but also at room temperature. The interaction energy among water moleculeshas also been estimated from van't Hoff's relationship. The detailed structural information should help to develop reliable force fields for molecular modeling of liquid water.     

二氧化硫溶于水和酸性溶液的化学状态研究

采用拉曼光谱技术，对SO₂溶于水和酸性溶液的化学状态进行了研究。测定出SO₂的特征拉曼光谱(1147 cm^-1)，表明SO₂是以SO₂·nH₂O形式存在于水和酸性溶液里。     

Lowest energy electronic transition in aqueous Cl(-) salts: Cl(-) → (H2O)6 charge transfer transition

We use UV resonance Raman spectroscopy to probe the lowest energy allowed electronic transitions of aqueous solutions containing Cl(-) salts. We show that the waters hydrating the Cl(-) are involved in charge transfer transitions that transfer electron density from Cl(-) to the water molecules. These charge transfer transitions cause significant change in the H-O-H bond angle in the excited state, which results in a strong enhancement of the preresonance Raman intensity of the water bending modes. Our work gives the first insight into the lowest allowed electronic transition of hydrated Cl(-).